What is the meaning of "v'Yigal ka'Mayim Mishpat"?
Rashi: Do this, and I will desire you. The Mishpat that you covered and hid will be Meguleh (revealed), and will flow amidst you like water.
Radak: V'Yigal is like Galos (flowing) water. There is a Patach under the Gimel; this shows that it is from the root Galal.
Malbim: This is like "Aso Tzedakah u'Mishpat Nivchar la'Shem mi'Zevach" (Mishlei 21:3). Mishpat is Bein Adam l'Chavero, and Tzedakah is Bein Adam la'Makom. Mishpat is planted in man's Sechel. Man's nature is to be civil. He needs Mishpat for society to last. Therefore [Mishpat] is compared to Gulos (ponds of) water. The source flows by itself, and goes outside. So Mishpat will flow from the source of Sechel and man's nature.
What does the verse say about Tzedakah?
Rashi: It will flow like a great river. Radak - it flows quickly. So I desire that Mishpat and Tzedakah go. Do not stop and detain it and leave it on the ground, and offer your Korbanos to Me - I do not desire this!
Malbim: Tzedakah (Bein Adam la'Makom) is not found in man's nature. He receives the Mitzvos from Hashem. This is like a river whose water is not in (from) it itself, rather, it gathers from water that is not from the river itself, rather, from mountains and external sources. So Tzedakah will come from outside (from Hashem). River water will not flow like a source to fill other [streams] and gather, only in the river. So the primary act of Tzedakah is perfection of the Nefesh itself. It is like a strong river, i.e. the primary ascent for the Regel and Korbanos is to learn Hashem's Chukim and Mishpatim, in order to learn to fear Hashem Elokecha. Tzedakah and Mishpat are the desired end, and not Korbanos!